Stars

Combined view of the galaxy SDSS J1448+1010 seen by ALMA and Hubble (Image ALMA (ESO/NAOJ/NRAO), J. Spilker et al (Texas A&M), S. Dagnello (NRAO/AUI/NSF))

An article published in “The Astrophysical Journal Letters” reports a study on the galaxy SDSS J1448+1010. A team of researchers used the ALMA radio telescope, the Hubble Space Telescope, and other instruments to examine it and found that no more stars are forming inside it. After analyzing the observations collected, they concluded that this is due to the fact that SDSS J1448+1010 is the result of a galaxy merger in which a large part of the hydrogen that forms the stars was ejected as a result of the gravitational effects suffered in the course of that event. In fact, the researchers discovered what was defined as a tidal tail formed by the ejected materials, which also include stars.

The dwarf galaxy NGC 1156 seen by Hubble (Image ESA/Hubble & NASA, R. B. Tully, R. Jansen, R. Windhorst)

An image captured by the Hubble Space Telescope portrays the dwarf galaxy NGC 1156, a truly unique object because it’s an irregular dwarf galaxy that has various characteristics that belong to different classes of galaxies. Typically, galaxies that are out of the ordinary are the result of interactions or mergers, which are sometimes still in progress and offer the possibility to see the shapes of the original galaxies. NGC 1156 is among other things an isolated galaxy, and that means that there are no other galaxies close enough to affect its shape with a much higher force of gravity.

At the center the stars R136a1, R136a2 and R136a3 seen by the Zorro instrument in visible light

An article accepted for publication in “The Astrophysical Journal” reports a study on the star R136a1, perhaps the most massive known. A team of researchers pushed the Zorro instrument mounted on the Gemini South telescope to its limits to observe R136a1, or RMC 136a1. The results suggest that it’s less massive than previously estimated, as it was thought to be even more than 300 times the Sun’s mass. It remains a colossus given that the new estimate peaks in probability at 196 times the Sun’s mass. Two “siblings” may also be less massive than previously estimated, as this study estimates the mass of the star R136a2 to be about 151 times the Sun’s and the mass of the star R136a3 to about 155 times the Sun’s. Understanding these huge stars better helps to better predict their end and the chemical elements that will be created at that stage.

Artist's concept of a Neptune-sized planet orbiting a class-A star (Image courtesy Steven Giacalone, UC Berkeley)

An article published in “The Astrophysical Journal Letters” reports a study on the exoplanet HD 56414 b, a warm Neptune discovered orbiting an A-type star that has a mass almost twice the Sun’s. A team of researchers used detections conducted by NASA’s TESS space telescope to find a candidate exoplanet that was subsequently verified thanks to follow-up observations conducted with other instruments. This is a rare combination, as these massive stars usually have giant planets like Jupiter or even more massive ones.

Phases of the Great Dimming of Betelgeuse

An article accepted for publication in “The Astrophysical Journal” reports an analysis of the situation of the star Betelgeuse examining its recovery after what was called the Great Dimming. A team of researchers used a number of instruments including the Hubble Space Telescope and other ground-based and space observatories to reconstruct the history of that event and to examine its consequences. Betelgeuse is returning to what it was a few years ago but not exactly because the colossal coronal mass ejection, confirmed once again by this study, which caused the Great Dimming has also altered stellar cycles that had existed for at least two centuries.